Symptoms of tree nut allergy are the same as those for other food allergies, although the symptoms tend to be more severe than for other foods. The diagnosis of tree nut allergy also mirrors that of other food allergies. Avoidance of all tree nuts is the mainstay of treatment of tree nut allergy – treatment of an allergic reaction to tree nuts involves the use of injectable epinephrine and antihistamines. Unlike other common food allergies, tree nut allergy is not frequently outgrown, especially when the allergic reactions experienced are severe.
WalnutsWalnuts are the most common tree nut allergy, especially English walnuts. Many people are allergic to walnut pollen, which causes symptoms of allergic rhinitis, but this doesn't mean that the person is also allergic to the tree nut. Walnut allergens are similar in structure to those allergens found in pecans, cashews, Brazil nuts, castor beans, cottonseed and mustard. Therefore, people with a walnut allergy may experience allergic reactions to these other foods.
CashewsCashews are the second most common tree nuts to cause food allergies. The oil found in the nutshell of the cashew is known to cause contact dermatitis, and is related to the oils found in the leaves of poison oak and in the skin of mangoes. Cashew allergens are similar in structure to palm oil, macadamia nuts, peas, soybean and walnut. Therefore people with a walnut allergy may experience allergic reactions to these other foods.
AlmondsAlmonds are the most popular tree nut consumed in the United States, and the third most common tree nut allergy. Almonds are commonly found in food processing, and are unexpected ingredients in breakfast cereals, granola bars, and baked goods. Almond allergy may predispose a person to other tree nut allergies, especially pistachio nuts.
HazelnutAllergy to hazelnut is more common in Europe than in the United States. Hazelnut pollen is a common cause of seasonal hay fever, and it appears that a person with hazelnut pollen allergy is at risk for food allergy to the tree nut itself. Hazelnut is also related to birch pollen, and therefore people with birch pollen allergy may experience oral allergy symptoms with eating hazelnuts. People with hazelnut allergy may also be allergic to coconut, cashews, peanuts, and soybean given the similarity between the allergens in these foods.
PecansPecans are a common food in the southern United States, but less common elsewhere in the world. Pecan affects approximately 1 in 10 people with tree nut allergies. People with pecan allergy are at risk for allergies to walnut, given the similarities between the allergens in these tree nuts.
ChestnutsChestnut allergy may be experienced by people with latex allergy and avocado allergy, given the similarity between the allergens found in latex and these foods. Oral allergy symptoms from eating chestnuts can also be experienced by those with allergy to mugwort pollen, apples and peaches.
Brazil NutsAllergy to Brazil nut is uncommon, probably because these are not commonly eaten tree nuts. It is possible that allergy to Brazil nuts will increase in the future, since genetically modified soybeans accidentally have proteins similar to those found in Brazil nut allergen. People with Brazil nut allergy may also be allergic to walnuts.
Pine NutsPine nut is a common food in southern Europe, but less common in other parts of the world. Pine nuts are an ingredient in pesto sauce, which is an example of a "hidden ingredient" of which few people are aware. It is theoretically possible for a person with pine pollen allergy to be allergic to pine nuts, given that allergens are similar between the two.
Macadamia NutsMacadamia nuts are common foods in Hawaii and the tropics, and are a novelty food elsewhere in the world. There is significant cross-reactivity between the allergens in macadamia nuts and cashews, so a person is likely to be allergic to both of these tree nuts.
PistachiosPistachios are relatively commonly reported tree nuts to cause food allergy symptoms, and are cross-reactive to cashews and mangoes. Hay fever to the pollen from the Parietaria weed, found in Europe, appears to predispose to pistachio allergy.
CoconutsCoconut allergy is rare, and they are only distantly related to other tree nuts. However, coconut allergen is similar to those allergens found in hazelnuts and walnuts, and therefore a person allergic to these tree nuts may also be allergic to coconut.
Roux KH, Teuber SS, Sathe SK. Tree Nut Allergens. Int Arch Allergy Immunol. 2003; 234-244.
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